Multipotent stem cells and more developmentally restricted precursors have previously been isolated from the developing nervous system, and their properties analyzed by culture assays in vitro and by transplantation in vivo. My laboratory has continued its analysis of embryonic stem cells and the factors regulating their differentiation into neurons, astrocytes and oligodendrocytes. Our current work is split between studying neural stem and progenitor cells, growing and characterizing human and mouse ES cells and developing new tools to study these cell populations. Our focus on ES cells is based on the realization that translating our findings to the clinical arena will require developing a reliable and reproducible source of cells. Our work on neural stem and progenitor cells is focused on identifying novel genes or novel roles of known genes, that may regulate the developmental process and extending the analysis of the behavior of stem cells in adult models of injury and disease. A long-term plan is to develop rat transgenic models, rat ES cell lines, and in-utero transplant paradigms. Recent results include a) Demonstrating neural differentiation of human ES (embryonic stem) cells b) Demonstrating a role for Nkx2.2 (Homeodomain protein) and ngn-3 (neurogenin-3) in regulating oligodendrocye differentiation c) Showing that Hes-1 (enhancer of split homologue), Hes-5 and BMP?s (Bone morphogenetic protein) regulate astrocyte differentiation from glial progenitor cells d) Identifying markers for neural stem cells e) Developing a stem cell microarray f) Generating a transgenic rat Together these results provide a strong basis for understanding how stem and precursor cell differentiation is regulated. Our model of differentiation suggests a sequential acquisition of differentiation markers. Our future work will focus on extending these observations and understanding how stem cells age.